Hard disk drives (HDDs) rotate magnetic disks and drive head gimbal assemblies (hereinafter referred to as HGAs) at high speed, in response to requests for large capacity, high recording density, and high-speed accessing. Rotation at such high speeds can cause fluctuation of air (turbulence) to buffet the magnetic disks and HGAs. This turbulence buffeting can disturb positioning a head on a magnetic disk. This is because the turbulence occurs at random and it is difficult to estimate its magnitude and cycle so that swift and accurate positioning control of the recording and reproducing head will be complex and difficult. Also, the turbulence buffeting may cause a noise to impair the quietness of the device.
Another problem caused by influence of the air within the device due to the high speed rotation other than the foregoing is increase in electric power consumption. When a magnetic disk is rotated at high speed, the air around the disk is dragged and rotated together. On the other hand, the air apart from the magnetic disk remains still, so that shearing force arises therebetween to become a load against the rotation of the disk. This is called as a windage loss, which becomes larger as the disk rotates at higher speed. In order to rotate the disk at high speed against the windage loss, a motor will require a larger output and electric power.
As the above-described turbulence and windage loss are proportional to the density of the gas within the device, there is an idea to reduce the turbulence and windage loss by enclosing low density gas instead of air in a hermetically sealed HDD. Hydrogen, helium, and the like are exemplified as the low density gas, but helium is optimum because it is effective, stable, and safe in considering actual use. HDDs with sealed helium gas may overcome the above-described problems and accomplish swift and accurate positioning control, electric power saving, and satisfactory quietness.
However, molecules of helium are extremely small and a diffusion coefficient of helium is large. Therefore, there has been a problem that enclosures used in usual HDDs are poorly sealed so that helium gas leaks easily during normal use.
In order to make it possible to hermetically seal low density gas like helium gas, a technique disclosed in U.S. Patent Application Publication No. 2005/0068666 “Patent Document 1”) has been suggested. Patent Document 1 discloses a magnetic disk device in which a hermetic connection terminal (feedthrough) for connecting an FPC assembly inside the enclosure and a circuit board outside the enclosure is attached to an opening of the base and the enclosure is hermetically sealed by a cover. With respect to the joint of the base and the cover which is a section for the helium inside the enclosure to be likely to leak therethrough, the aluminum die-casted base and the aluminum cover are laser-welded so as to securely seal the joint.
With respect to the attaching section of the feedthrough, which is another section through which the helium inside the enclosure is likely to leak, the feedthrough is constituted by a header and a plurality of pins secured to the header with insulating sealants of glass or the like, and the header is soldered to the rim of the opening on the bottom of the base so as to completely seal the attaching section.
In addition, many structures for making a terminal airtight have been known. Japanese Unexamined Patent Application Publication No. 2007-250805 (“Patent Document 2”) discloses an example of a surface mounting hermetic terminal.
As described above, a conventional feedthrough used in a hermetically sealed HDD comprises a plurality pins secured to a head with insulating sealants like glass and projecting largely out from the header upward and downward. These pins protrude from the bottom of the device, and have thin shapes and small rigidity. Therefore, in handling the feedthrough in manufacturing an HDD, an inadvertent force or shock is occasionally applied to the pins to bend them or damage the rim sealants. A bended pin reduces the reliability of the device because it may raise contact failure with a connector. A damaged insulating sealant reduces the reliability of the device as well because it may cause helium to leak. Particularly, an excessive force may be applied to the pins in a connecting step of the feedthrough and connectors inside and outside of the HDD; it has been afraid that the manufacturing efficiency, the yield, and the reliability of the HDD may be reduced.
For a hermetic terminal to be used in surface mounting like the hermetic terminal disclosed in the Patent Document 2, a hermetic terminal in which the end face of a conducting part to transmit signals is flush with the surface of its main body has been known. Such a terminal structure may prevent the pins or the rim sealants from being damaged due to an external force to the pins since the pins do not largely protrude from the header.
However, the hermetic terminal disclosed in the Patent Document 2 has a structure asymmetrical to the direction of the axes of the pins, which has been a factor to interfere with efficient manufacture of the hermetic terminal. Consequently, an efficient manufacturing method of a feedthrough to be used in an HDD having a sealed enclosure is desired. The connection between the hermetic terminal and terminals inside and outside of the enclosure is made by wire bonding or conductive joining materials so that high airtightness cannot be expected and it is difficult to apply such a terminal structure to a feedthrough for a hermetically sealed HDD.
Accordingly, a technique is demanded for using a feedthrough easy in manufacture and handling and assuring easy and secure conductance between the feedthrough and the corresponding connectors.